Gas exchange

• What is the composition of the exoskeleton in terrestrial insects?

  It is made of chitin and a lipid layer
• Why do terrestrial insects not have lungs?

  They have a tracheal system for gas exchange
• What is a major challenge for terrestrial organisms regarding gas exchange?

  Balancing gas exchange with water loss
• What are the adaptations insects have to reduce water loss?

  • Small surface area to volume ratio
  • Lipid layer on exoskeleton
  • Spiracles that can open and close
• What is the function of spiracles in insects?

  They allow gas exchange and water evaporation
• How do spiracles help prevent water loss?

  They can open and close to regulate loss
• What are the three main structures of the tracheal system?

  Spiracles, trachea, and tracheoles
• What role do trachea play in insects?

  They are internal tubes for gas transport
• How do trachea remain open in insects?

  They have rings to prevent collapsing
• What is the function of tracheoles in the tracheal system?

  They deliver oxygen to respiring cells
• How does gas exchange occur in insects?

  Through simple diffusion and concentration gradients
• What creates the concentration gradient for gas exchange in insects?

  Respiring cells using oxygen and producing carbon dioxide
• What is mass transport in the context of insect gas exchange?

  Muscle contractions move gases in and out
• What happens to muscle cells during insect flight regarding respiration?

  They switch from aerobic to anaerobic respiration
• What is produced during anaerobic respiration in insects?

  Lactate or lactic acid
• How does lactate affect water potential in insect cells?

  It lowers the water potential of the cells
• What is the result of lower pressure in the tracheal system?

  It draws more air from the atmosphere
• What are the key factors for effective gas exchange in insects?

  • Large surface area from tracheoles
  • Short diffusion distance
  • Maintained concentration gradient
• What are the three key layers for gas exchange in a dicotyledonous leaf?

  • Stomata
  • Spongy mesophyll
  • Palisade mesophyll
• What is the plural form of stoma?

  Stomata
• What forms the gap known as a stoma?

  Two guard cells
• Where is the site of gas exchange in the leaf?

  At the stomata
• What gas diffuses into the leaf for photosynthesis?

  Carbon dioxide
• Where does carbon dioxide diffuse after entering the leaf?

  Into the spongy mesophyll
• Why does carbon dioxide diffuse into the spongy mesophyll?

  To maintain a concentration gradient
• Where does most photosynthesis occur in the leaf?

  Palisade mesophyll
• Why does the palisade mesophyll receive more sunlight?

  It is closer to the top surface
• What two types of tissue are found in the vascular bundle?

  Xylem and phloem
• What does the xylem transport?

  Water and dissolved mineral ions
• What does the phloem transport?

  Sucrose
• What shape are the cells in the palisade mesophyll?


  Long and oblong
• Why are palisade mesophyll cells packed closely together?

  To maximize light absorption
• What is the role of chloroplasts in palisade mesophyll cells?

  To absorb light for photosynthesis
• What gas diffuses out of the stomata?

  Oxygen
• Why does oxygen diffuse out of the stomata?

  It is a product of photosynthesis
• When do stomata typically close?

  At night
• What happens to guard cells at night?

  They become less bent
• What are xerophytic plants?

  • Plants that survive in harsh conditions
  • Adapted to limited water availability
  • Have features to reduce water loss
• What adaptation helps reduce evaporation in xerophytic plants?

  Curling of the leaf
• How does curling of the leaf help xerophytic plants?

  Traps evaporated water, increasing humidity